Skip to main content

Questions tagged [radio-frequency]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0 votes
0 answers
10 views

Phase Slope Distance Calcuation

After trying to implement IFFT algorithms for phase-based ranging, as outlined in this very interesting and descriptive blog post; I've been getting horrendous results (orders of magnitude inaccurate),...
Hysan Happy's user avatar
0 votes
0 answers
70 views

Why does this RLC behavior differ from what equations predict?

In order to better understand RLC behavior under current sources, I constructed the simple circuit below and attempted to analyze it. However, my equations do not agree with simulation results. The ...
SRobertJames's user avatar
0 votes
1 answer
33 views

Phase-Based Ranging

I've been reading a lot about Phase-Based Ranging (PBR), and it's all starting to become very intuitive. BUT; There is one technical, but extremely important, detail that seems to escape me. When the ...
Hysan Happy's user avatar
0 votes
2 answers
63 views

Are these levels of RF radiation harmful?

I live on the top floor of a building that has four 5G antennas on the roof. The house is curved, and from my viewpoint, I can partially see one of the antennas pointing towards me. Curious about the ...
Armands L.'s user avatar
0 votes
1 answer
56 views

Prime operator for sinusoidal testing function in self-term approximation for Thin Wire using Method of Moments (MoM) $s_m^{'}(x_p)$?

I am implementing thin wire method of moments using W.Gibson's "Method of Moments in Electromagnetics". The approximation for self-term using piecewise sinusoidal basis function is given as ...
Ashish Magar's user avatar
1 vote
0 answers
23 views

Synchronous phase value for CERN LHC [closed]

How to find out that the value of the synchronous phase for CERN LHC in the case where beams undergo collision, and the RF cavities provide only longitudinal focusing with no net acceleration.
Harryddd09w's user avatar
1 vote
1 answer
28 views

Slice selection in MRI

Studying MRI, I found that excitation is done by applying B1 (RF) and Gz simultaneously. But, I think that if those are applied at same time, slice selection cannot be done correctly because Gz will ...
COTHE's user avatar
  • 43
0 votes
2 answers
73 views

Book Recommendation about radio frequency antennas and satellites

I have recently obtained a job in the field of radio frequency antennas and satellites, and I am interested in delving deeper into the subject. Could you recommend any books that cover these topics ...
0 votes
1 answer
82 views

Why is 180 degree pulse applied after half echo time (TE) in Spin Echo sequence?

The definition of Echo Time from Radiopaedia: The echo time (TE) refers to the time between the application of the radiofrequency excitation pulse and the peak of the signal induced in the coil. It ...
HelpNeederStudent's user avatar
0 votes
2 answers
85 views

Gravitational waves vs ULF Radio waves

During the recent merger of two Neutron stars the lead up to the merger was detected as gravitation waves. This was the merger of two spinning bodies that had very strong magnetic fields and they were ...
Michael Mcgarry's user avatar
0 votes
0 answers
55 views

Is the Fourier Transform a reliable way to infer the physical phenomena producing an RF signal?

Consider the following thought experiments: Scenario 1: A person standing far away shines 3 light beams at you, each beam having a narrow spectral distribution centered around different frequencies F1,...
codecitrus's user avatar
0 votes
1 answer
54 views

Can I recover the physical wavelengths present in a light source from a time-series measurement of its amplitude?

Consider a mixture of different wavelengths being emitted from the same point (ex: a star). This light consists of a mixture of wavelengths and intensities at each wavelength. When measuring the ...
codecitrus's user avatar
0 votes
0 answers
18 views

What exactly decides the TTC frequency selections of X-band for deep space missions, C band for geostationary , and S band for LEO missions?

Data rates are higher in X-band, but considering free space path loss and atmospheric attenuation(diffraction I'm assuming is significant here), won't lower frequencies stand a better chance? Again, ...
Gayathri Aishwarya E's user avatar
0 votes
1 answer
63 views

How to measure time varying electric field strength accurately in space and time?

I would like to know of any techniques that can be used to measure the electric field strength precisely and accurately in both time and space. I know that there will be physical/ practical ...
Christian's user avatar
  • 113
0 votes
1 answer
50 views

Question about CPU manipulation with RF waves [closed]

Is it possible that by sending a specifically modulated RF wave, you can manipulate the flow of electricity to the CPU, and maybe cause binary code Execution? Like typing something like Hello?
19216811's user avatar
0 votes
2 answers
53 views

How to increase the angle of light (without going from a higher to lower index of refraction)?

I would like a device to spread out/increase the angle of rays in a light source. In other words, I would like to reproduce the behaviour of light traveling from an area of higher to lower index of ...
Tom's user avatar
  • 1
0 votes
0 answers
10 views

Does the RF magnetic field have to be uniformly constant for a coherent EPR signal

Consider a loop gap resonator for electron paramagnetic resonance which has static (but sweepable) magnetic field in one direction, "x", and a GHz RF magnetic field in a direction "z&...
Tunneller's user avatar
  • 131
1 vote
0 answers
48 views

When does Lorentz reciprocity not apply to an EM system?

I'm trying to understand the limits of when Lorentz reciprocity does and doesn't apply to a given system. I know that it only applies to linear systems, but based on a couple of examples I believe ...
Christian's user avatar
  • 113
1 vote
1 answer
65 views

Is there an intuitional way to tell which physical quantities are angular frequency and which are frequency?

Such as the natural linewidth is defined to be angular frequency, while the absolute frequency of laser is frequency. By far I haven't found a good way not to learn it by roting. Would anyone be ...
QubitTy's user avatar
  • 31
1 vote
1 answer
47 views

How a does a RF magnetic field interact with trapped atoms in evaporative cooling?

In the paper “Evaporative Cooling of Trapped Atoms,” [Advances in Atomic Molecular And Optical Physics 37, 181–236 (1986)] by Wolfgang Ketterle and N. J. Van Druten, they claimed the matrix element ...
Hsu Bill's user avatar
  • 388
6 votes
3 answers
656 views

Impedance at Feed Point and End of Antenna

Watching this pretty great video from 1947 about antenna fundamentals. I have a question about one part of it though. The video states that the impedance at the feed point of the antenna is 72 ohms, ...
vigilante_fresh's user avatar
2 votes
1 answer
121 views

Antennas and Wavelength

I'm clearly missing something here, but I'm trying to grasp basics of how antennas work. Relating it to standing waves on a string of length L, the lowest frequency possible is a wavelength of 2L, due ...
vigilante_fresh's user avatar
1 vote
0 answers
29 views

Wireless Power Transfer Modelling

I am trying to develop an analytical model for RF wireless power transfer from an external antenna to an implant antenna, embedded inside layers of lossy tissue. The external antenna will be ...
PikaPika's user avatar
1 vote
0 answers
33 views

How would we create a device to detect communication using the x-ray and gamma bandwidth? Like a radio. But x-ray gamma spectrum [closed]

I realize the dipole would have to be small enough (in the nucleus of an atom range) and we don't have any mechanism that is small enough to demodulate the frequencies at this rate. But is there some ...
ZiiZii's user avatar
  • 11
1 vote
1 answer
193 views

How does one pick Echo time (TE) in MRI machine?

The definition of echo time (TE) in MRI is the time difference between a 90-degree RF signal and the echo peak, which feels like an intrinsic property of the proton. How can we even control how long ...
yupbank's user avatar
  • 181
0 votes
0 answers
45 views

Mathematical Modelling of Wireless Power Transfer

I am trying to understand the interaction between a transmitting antenna with a certain transmitting power (denoted PTX in the diagram) and how the radiation pattern of the TX antenna is affected by a ...
PikaPika's user avatar
2 votes
2 answers
358 views

How does radio wave get reflected?

Actually recently I posted a question in h-bar ($\hbar$) relates to radio wave reflection from mirror, and one of the user replied that it can't, only ionosphere can reflect it, so my question what is ...
आर्यभट्ट's user avatar
2 votes
3 answers
198 views

Feynman physics on least time of light

What does light checks all paths mean by Feynman? Especially the statement is labeled by yellow. Why there is only one path that leads radiowaves to D’? And how wave check all paths, that is, why it ...
Xiang Li's user avatar
  • 329
1 vote
1 answer
56 views

What is physically happening in a medium in which an evanescent wave is propagating?

Let's consider for instance a metal, for which the dielectric function reads: $\epsilon = 1 - \frac{\omega_{p}^{2}}{\omega^{2}}$ where $\omega_{p}$ is the plasma frequency. The dispersion relation for ...
Emanuele Giordano's user avatar
0 votes
1 answer
37 views

Can radio waves with multiple frequencies have the same power?

I was watching data from a spectrum analyzer that shows the frequency of the wave and its power in dBm. I noticed that all frequencies were operating at the same power; however, I don't understand how ...
Belal Bahaa's user avatar
0 votes
0 answers
29 views

Interferometry maximum wavelength for a set of baseline lengths

I am trying to understand phase ambiguity resolution for interferometry. Unfortunately, all I have are old power points and not really any notes or textbooks on the subject. I have found in a power ...
Graham Chapman's user avatar
1 vote
1 answer
36 views

Is there an optical/electromagnetic equivalent to the mechanical lever?

From Wikipedia: "Levers can be used to exert a large force over a small distance at one end by exerting only a small force (effort) over a greater distance at the other." Is there any ...
Ian Daniel Sooknanan's user avatar
2 votes
2 answers
82 views

Cryogenic and vacuum safe cable labeling or tagging

Not the most in depth of physics questions, yet this feels like the right community for trying to crowd-source this type of expertise. Essentially it is a question for those of you experienced with ...
user129412's user avatar
  • 1,521
0 votes
1 answer
49 views

Mechanism of NMR

I am doing research into NMR right now in several different sources, and it seems as if there are two competing models which are used to describe how radio waves can impact nuclear spins. The first ...
slithy_tove's user avatar
1 vote
1 answer
79 views

Implementation Question about Thin Wire Method of Moments

I am currently trying to implement a simple $1 \textrm{D}$ thin-wire method of moments code in Python to practice E&M and numerical methods. I am following Gibson's "The Method of Moments in ...
Brasswyrm's user avatar
0 votes
1 answer
59 views

Time difference of arrival between radar pulses

Consider the following geometry: Where $\bar{s} = (s_x,s_y)$ is an object of interest, and $\bar{r_c}$ is the location of the radar. Let the echo delay time of a radar pulse to the scene center be $...
DarkLink's user avatar
  • 169
0 votes
1 answer
1k views

What type of equipment could generate interference on the 1.6ghz spectrum [closed]

From the perspective of physics - other than wireless computer network devices - what domestic or domestic or commercial equipment could generate seemingly random interference on the 1.6ghz range? ...
Aaargh Zombies's user avatar
1 vote
2 answers
208 views

How do lasers work if the phase shift from reflection is 180 degrees?

I am having a hard time wrapping my head around the phase shift that is imposed by reflection. I'm specifically thinking about things like visible light of off mirrors or RF reflecting off of silver, ...
Ender's user avatar
  • 33
11 votes
3 answers
3k views

If we have a cosmic microwave background should't we also have a cosmic radio wave background?

I'm a layman in physics, but here is what I understand: What we see in the sky with naked eyes is a map of electromagnetic waves in the frequency visible to the human vision. But that kind of ...
Werex Zenok's user avatar
0 votes
0 answers
114 views

Reflection of power at low frequencies?

Assume you have an AC signal source outputting $0\,\text{dBm}$ of power and connected to that are two resistors one of $50 \,\Omega$ and another $100 \,\Omega$. The reflection coefficient is given by: ...
Dylan Muller's user avatar
0 votes
1 answer
51 views

How does the echo of a radio wave from Venus depend on the rotation speed and direction of the planet?

In this paper from around 1960 scientist used echos of radio waves from the Venus' surface to determine its rotational speed and direction. How can the rotation of Venus affects the echo of the radio ...
MOON's user avatar
  • 947
11 votes
4 answers
2k views

Why do we even need RF cavities to accelerate particles?

Wouldn't it be easier to just apply a constant $E$ field along the beam axis? This would avoid all kinds of problems like synchronicity, phase change etcetera. Addendum. What puzzles me the most is ...
ric.san's user avatar
  • 1,644
1 vote
0 answers
25 views

Is there any mathematical model of how does rain & other weather conditions impact the radio link?

I'm looking through UAV radio-communication process and wondering if there are any formulas, describing how does the air pressure and weather itself (rainy & snowy conditions) affect the radiolink ...
Konstantin Mironov's user avatar
2 votes
0 answers
42 views

Radiowave diffraction

When a far field propagated radio wave encounters an obstacle such as a mountain does the radio wave actually bend around the mountain? In other words should my receiving antenna on the other side of ...
Roger's user avatar
  • 21
1 vote
4 answers
309 views

Superposition of EM waves and "magic" behind tuned receiver circuit

I'm struggling to understand how the receiver circuit (eg. FM radio) is able to extract a particular frequency out of the sum of all received frequencies by its antenna? I've checked dozen of websites,...
Nenad Strainovic's user avatar
0 votes
1 answer
23 views

Frequency upconversion of pulses shorter than 1 IF period

I have a rather elementary frequency upconversion/mixer question, perhaps so simple that it does not warrant a real question but rather just a reference to a website/tutorial (that I have not been ...
user129412's user avatar
  • 1,521
2 votes
4 answers
2k views

How are sidebands generated in an AM signal?

I can't understand how sidebands get generated, even after reading this wikipedia page: https://en.wikipedia.org/wiki/Sideband#Amplitude_modulation This is how I picture Amplitude Modulation in its ...
Dan's user avatar
  • 127
0 votes
1 answer
64 views

Scattering off upside-down parabolic reflector (radio frequency)

Suppose I have a steel frame parabolic reflector with a handful of steel wire supports. The size is approximately 10m high and 20m in radius. Assume the gaps in the triangular trusses are roughly 3m. ...
Jackson Walters's user avatar
8 votes
1 answer
604 views

Why is a magnesium flame changing color in an electromagnetic field?

On YouTube I have seen someone build a RF emitter (probably in the 10 MHz range with about 5000 Watts) and then use it to ignite magnesium strips. Magnesium usually burns with a bright white flame in ...
iblue's user avatar
  • 632
0 votes
1 answer
448 views

Do electrons in EM waves literally travel in space, or they just move like a rope being swung at an end

Electrons do actually move in a closed circuit as explained in this video: https://youtu.be/8gvJzrjwjds?t=85 They jump from atom to atom. But what about electromagnetic waves, or more specifically ...
Dan's user avatar
  • 127

1
2 3 4 5 6